This invention pertains to ribbon cassette for printers and more particularly to ribbon cassettes that are responsive to ribbon breakage for giving indications of such breakage.
Many present day printers are driven unattended by computers. Manufacturers are aware of this fact and have included end-of-ribbon sensing. In general, the printer includes a photoelectric assemblage having a light source and a light detector which coact with the ribbon in the casette. The end of the ribbon has either a reflective or transmissive region depending on the assemblage. When a certain condition is sensed such as the presence of light by the detector, an indication is given that the end of the ribbon has come. This indication stops the printing operation. While the end-of-ribbon problem has been solved, the ribbon breakage problem has generally been ignored.
In addition to requiring reliability, generally, there is a desire for good print quality. Given good print elements, ribbons and record media, print quality depends on the tension of the ribbon while printing. Not only does good tension improve print quality, but it also facilitates the take-up of spent ribbon. Therefore, most cassettes include ribbon tensioning. Examples of such ribbon tensioning can be found in U.S. Pat. Nos. 4,367,052; 4,373,824; 4,010,839; and 4,368,992. These patents teach the use of complicated ratcheting schemes to produce such tension.